Linear guide

ABSTRACT

A linear guide for transmitting a torque between a tubular housing, which is defined by a longitudinal axis and rotatable about the longitudinal axis, and a shaft, which is received in the housing and movable in the direction of the axis in relation to the housing, includes a bearing assembly received in the housing for support of the shaft and attached to the housing by swaging a housing portion. The bearing assembly has two bearing members and a set of rolling bodies disposed between the bearing members. One bearing member is constructed as bushing which is retained in the housing and defines a center axis which is oriented out-of-alignment with a normal upon a longitudinal shaft axis, and the other bearing member has a cup-shaped configuration to define a convex surface for support by a surface area of the shaft.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of prior filed copending U.S. applicationSer. No. 10/643,209, filed Aug. 15, 2003 which is a continuation ofprior filed copending PCT International application no. PCT/EP02/00675,filed Jan. 24, 2002, which designated the United States and on whichpriority is claimed under 35 U.S.C. §120 and which claims the priorityof German Patent Application, Serial No. 101 06 982.0, filed Feb. 15,2001, pursuant to 35 U.S.C. 119(a)-(d).

BACKGROUND OF THE INVENTION

The present invention relates to a linear guide for transmitting atorque between a tubular housing, which is defined by a longitudinalaxis and rotatable about the longitudinal axis, and a shaft, which isreceived in the housing and movable in the direction of the axis inrelation to the housing.

Linear guides for transmission of torques are used in the automobileindustry for example for guiding racks or for guiding steering spindlesin a steering column. Another use involves the guidance of gearshiftshafts or gearshift rails in the transmission of motor vehicles.

U.S. Pat. No. 3,427,656 describes a linear guide having sets of axialrolling bearings which are arranged in the area of a radial plane of ashaft and are held in a tubular housing. The axial rolling bearingssurround the shaft and have cup-shaped running disks for support on theshaft surface. As the shaft has a circular cross section, torque of theshaft cannot be transmitted to the housing. This conventional linearguide requires also the arrangement of a tensioning screw to pretensionthe sets of axial rolling bearings and to act in the area of a radialslot of the housing upon the housing.

German patent publication No. DE 196 19 449 A1 describes a linear guidehaving a rod or shaft with rollers bearing on the bearing surface of theshaft and which are rotatably supported in a carriage surrounding theshaft. The carriage is configured as a rectangular hollow profile withT-grooves that are exteriorly accessible, and by means of which otherdesired parts may be secured. For support of the rollers, bore holes areprovided at the side walls of the hollow profile where rotationalbearing, in particular roller bearings are disposed. Furthermore, atleast one roller, respectively the bearing support of the rollerrequires a control device, preferably a set screw for snug adjustment ofthe roller against the shaft.

German patent publication no. DE 37 30 393 A1 discloses a torquetransmitting connection for shaft parts that move axially within oneanother for use in a steering shaft of a motor vehicle. The linear guidehas balls as rolling members which are received free from play in innerlongitudinal grooves of the outer shaft part, on one hand, and in outerlongitudinal grooves of the inner shaft part, on the other hand. Inorder to compensate manufacturing tolerances and to realize a smoothrunning without a need for refinishing works, when the shaft parts moveaxially relative to one another, the balls must be arranged in racewaysof sheet metal which are placed in the longitudinal grooves and loadedradially under tension in relation to the longitudinal center axis ofthe shaft. Moreover, both shaft parts can be moved axially relative toone another only in a limited manner.

It would therefore be desirable and advantageous to provide an improvedlinear guide which obviates prior art shortcomings and which is simplein structure and cost-efficient while still being reliable in operationindependent on dimensional tolerances of the tubular housing and theaxially movable shaft.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a linear guide fortransmitting a torque between a tubular housing, which is rotatableabout a longitudinal axis, and a shaft, which is received in the housingand movable in the direction of the axis in relation to the housing,includes plural axial rolling bearings received in the housing insurrounding relationship to the shaft, wherein the plural axial rollingbearings are disposed in two radial planes in axial spaced-apartrelationship, wherein the axial rolling bearings in each of the tworadial planes have each two bearing members and a set of rolling bodiesdisposed between the bearing members, wherein one bearing member isconstructed as bushing which is retained in the housing and defines acenter axis which is shifted in parallel relationship at an offset to anormal of a longitudinal shaft axis, wherein the other bearing memberhas a cup-shaped configuration to define a convex surface for support bya surface area of the shaft.

As a consequence of the parallel shift of the bushing axis in relationto the shaft center, and in view of the convex cup-shaped surface of thebearing member and its support on the surface area of the shaft, thecontact point of the shaft is shifted so as to establish a rotationlever which causes a rotation of the bearing member, when the shaftmoves linearly. An adverse impact of dimensional tolerances can beeliminated by a tolerance-independent positioning of the axial rollingbearing in relation to the shaft.

According to another aspect of the present invention, a linear guide fortransmitting a torque between a tubular housing, which is rotatableabout a longitudinal axis, and a shaft, which is received in the housingand movable in the direction of the axis in relation to the housing,includes plural radial needle bearings received in the housing insurrounding relationship to the shaft, wherein the plural axial rollingbearings are disposed in two radial planes in axial spaced-apartrelationship, wherein the radial needle bearings in each of the tworadial planes have each two bearing members and a set of rolling bodiesdisposed between the bearing members, wherein one bearing member isconstructed as needle bushing which is retained in the housing anddefines a center axis which is shifted to a normal of a longitudinalshaft axis, wherein the other bearing member has a cup-shapedconfiguration to define a convex surface for support by a surface areaof the shaft, and includes bearing journal which is surrounded by theneedle bushing, with the rolling bodies arranged in the needle bushingand constructed as needles.

Hereby, the center axis of the needle bushing may be shifted in parallelrelationship to the normal at an offset, or, as an alternative, thecenter axis of the needle bushing may be inclined at an angle inrelation to the normal to have a same effect.

A linear guide In accordance with the present invention is thus able totransmit torques but also to transmit tilting moments. When defining thelongitudinal shaft axis as X-axis and the two axes which extendperpendicular to the X-axis and perpendicular to one another as Y-axisand Z-axis, moments about the X-axis are torques which are transmittedfrom the shaft onto the housing. As the bearings, which surround theshaft, are disposed in two radial planes in axial spaced-apartrelationship, moments about the Y-axis and moments about the Z-axis,which are tilting moments, can be further be transmitted from the shaftonto the housing.

As the housing is thin-walled, when used as steering tube, itselasticity can be exploited as pretensioning element. In this case, therespective support bearings are mounted initially in the housing withovermeasure in relation to the center. As the shaft is then insertedinto the housing, the housing is widened, i.e. the steering tubeundergoes an elastic deformation, to realize the intended pretensioningeffect. The need for a special tensioning screw, as required in theprior art, is thus no longer necessary.

The shaft of the linear guide may be a steering column spindle ofpolygonal configuration, e.g. of triangular, tetragonal, or square crosssection, wherein the surface area has a concave shape, and wherein atleast two longitudinal sides adjoining one another in circumferentialdirection have each a concave surface area. As a consequence of theconcave surface areas, the load-carrying capability of the bearing isenhanced.

The invention allows the use of complete bearing kits with rollingbodies and raceways, so that it is no longer necessary to incorporatethe raceways the housing.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be morereadily apparent upon reading the following description of currentlypreferred exemplified embodiments of the invention with reference to theaccompanying drawing, in which:

FIG. 1 is a perspective illustration of one embodiment of a linear guideaccording to the present invention, illustrating a cross section in anarea of a bearing plane to show axial rolling bearings incorporatedtherein;

FIG. 2 is a cross sectional view, on an enlarged scale, of the linearguide of FIG. 1;

FIG. 3 is a fragmentary cross sectional view of a variation of a linearguide according to the present invention with modified axial rollingbearing;

FIG. 4 is a fragmentary cross sectional view of still another variationof a linear guide according to the present invention with arolling-contact bearing including of needles and balls; and

FIG. 5 is a fragmentary cross sectional view of yet another variation ofa linear guide according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the Figures, same or corresponding elements are generallyindicated by same reference numerals. These depicted embodiments are tobe understood as illustrative of the invention and not as limiting inany way. It should also be understood that the drawings are notnecessarily to scale and that the embodiments are sometimes illustratedby graphic symbols, phantom lines, diagrammatic representations andfragmentary views. In certain instances, details which are not necessaryfor an understanding of the present invention or which render otherdetails difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is showna perspective illustration of one embodiment of a linear guide accordingto the present invention, including a shaft 1, a housing 2, and aplurality of axial rolling bearings, generally designated by referencenumeral 3 and constructed as ball bearings. The shaft 1 has a generallysquare cross section with four longitudinal sides, wherein eachlongitudinal side is formed with a concave surface area 4 which extendswith constant cross sectional dimensions in longitudinal direction ofthe shaft 1. The linear guide according to the present invention may besuitable as steering shaft or steering column for a motor vehicle,whereby the tubular housing 2 may be suitable as steering tube and theshaft 1, which is axially movable in the housing 2, may be constructedas steering spindle.

The housing 2 is configured in the form of a square tube and has innercross sectional dimensions which are greater than the shaft size. Theshaft 1 is inserted axially into the housing 2 and supported by theaxial rolling bearings 3. The linear guide has hereby two radial bearingplanes which are disposed in axial spaced-apart relationship. In thearea of each bearing plane, there are disposed four axial rollingbearing 3 about the periphery of the tubular housing 2. The housing 2 isformed hereby with radial bores 5 which extend continuously from one endto the other end of the housing 2, wherein each bore 5 is placed inneighboring relationship to the a concave surface area 4 of the shaft 1.

Each axial rolling bearing 3 includes a bearing member in the form of arunning ring or running disk 6, a C-shaped bushing 7, and a set ofrolling bodies 8 which are arranged between the running disk 6 and thebushing 7 and designed as balls. The disk 6 has a cup-shapedconfiguration and has a convex cup-shaped surface 9 in confrontingrelationship to the shaft 1 for support in the adjacent concave surfacearea 4 of the shaft 1. Suitable osculation conditions result in a pointcontact 10 between the disk 6 and the shaft 1.

The cup-shaped running disk 6 is supported via the orbiting set ofrollers 8 on the bushing 7, which is a shaped component made through aprocess without material removal and includes a raceway for the set ofrolling bodies 8. The bushing 7 is press-fitted in the respective bore 5of the housing 2, whereby the bore 5 is so arranged in the housing 2that the center axis 11 of the bushing 7 is shifted at an offset “a”(FIG. 2) in parallel relationship to a normal 12 oriented in the bearingplane upon the longitudinal axis of the shaft 1. As a consequence ofthis offset, the contact point 10 is shifted by the distance “b”relative to the normal 12 to thereby form a rotation lever. Thus, as theshaft 1 moves linearly within the housing 2, this rotation lever causesa rotation of the running disk 6 about the contact point or realizedcontact line 10.

The axial rolling bearings 3 can be properly positioned, regardless oftolerances, relative to the shaft during installation in the tubularhousing 2 as follows: The axial rolling bearings 3 are press-fitted inthe bores 5 deep enough to establish a desired contact upon the shaft 1.A proper positioning can be determined by the degree of the forceincrease.

FIG. 1 shows a cross section in the forward bearing plane. In order toproperly position the shaft 1 in the housing 2, at least one furtherbearing plane is required in axial spaced-apart relationship so as torealize a play-free torque transmission in both circumferentialdirections of the linear guide. FIG. 1 shows in an area of a rearwardbearing plane the arrangement of two bushings of pertaining axialrolling bearings 3. The shaft 1 can be positioned in all axis directionsin such a square profile by providing at least two axial rollingbearings 3 for each bearing plane.

Of course, the shaft 1 may have a configuration different from thesquare profile as shown in the drawing. For example, the shaft 1 mayhave a triangular profile, a polygonal profile, a hollow profile, or asolid profile. Also the provision of a round shaft may be conceivable,although torque cannot be transmitted.

FIG. 3 shows a fragmentary cross sectional view of a variation of alinear guide according to the present invention. The description belowwill center on the differences between the embodiments. In theembodiment of FIG. 3, provision is made for an axial rolling bearing,designated by reference numeral 13 and having a bushing 14 and aresilient rubber ring 15 which is received in the bushing 14. Supportedon the rubber ring 15 is a bearing disk 16 to form a raceway for the setof rolling bodies 8. The rubber ring 15 operates hereby as an element tocompensate for dimensional tolerance and to absorb noise.

FIG. 4 shows a fragmentary cross sectional view of still anothervariation of a linear guide according to the present invention. Thedescription below will center on the differences between theembodiments. In the embodiment of FIG. 4, the linear guide isconstructed here, instead of a pure axial rolling bearing, with arolling-contact bearing assembly that combines an axial rolling bearingwith a set of rolling bodies 19 and a radial needle bearing 18 withneedles. The radial needle bearing 18 is provided with a needle bushing17 and a set of rolling bodies in the form of the needles for support ofa bearing journal 20 during linear movement in relation to the housing2. The bearing journal 20 forms part of T-shaped bearing member and issecured to the running disk 6 or formed in one piece therewith, wherebythe needles are disposed radially between the bearing journal 20 and theneedle bushing 17. The set of rolling bodies 19 of the axial rollingbearing is disposed axially between the bottom of the needle bushing 17and an outer end surface of the bearing journal 20 and provided foraxial support of the bearing journal 20 as well as reducing frictionduring rotation of the bearing journal 20.

FIG. 5 shows a fragmentary cross sectional view of yet another variationof a linear guide according to the present invention. The descriptionbelow will center on the differences between the embodiments. In thisembodiment, provision is made for radial needle bearing, designated byreference numeral 22. The needle bearing has a set of rolling bodies inthe form of needles and a needle bushing 21 which is constructed insurrounding relationship to the bearing journal 20 and the needles. Theneedle bushing 21 has a bottom which is formed with in an inwardconvexly arched elevation 23 for axial support of the bearing journal20. In this way, friction is reduced, as the bearing journal 20 rotates.

The needle bushing 21 defines hereby a center axis 11 which extends atan inclination at an angle α to the normal 12 upon the longitudinal axisof the shaft 1, thereby establishing also a rotation lever, as aconsequence of the distance b between the normal 12 and the contactpoint 10, for the running disk 6 to realize a rotation of the bearingdisk 6 about the contact point 10 during linear movement of the shaft 1.

In all embodiments each of the respective bearing may be attached to thehousing 2 by means of a swaging 24 (FIGS. 4 and 5) of the housingmaterial or by means of a split resilient ring disposed in bore 5 ofhousing 2. As shown in FIGS. 4 and 5, the swaging 24 is realized byshaping the housing 2 adjacent to the bore 5 to have a taperedconfiguration to reduce the diameter of the bore 5. Thus, once the axialrolling bearing 13 is positioned in the bore 5, the bushing 14 isprevented from migrating radially outwards by the presence of the swagedarea 24.

To realize a pretension of the linear guide, it is conceivable to pressone or more bearings further than the shaft size would require, forexample, after insertion of a tool with dimensions that are smaller thanthe shaft. After extraction of the tool, the shaft is inserted in thehousing which then acts as pretensioning element.

While the invention has been illustrated and described in connectionwith currently preferred embodiments shown and described in detail, itis not intended to be limited to the details shown since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention. The embodiments werechosen and described in order to best explain the principles of theinvention and practical application to thereby enable a person skilledin the art to best utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims and their equivalents:

1. A linear guide for transmitting a torque between a tubular housing,which is defined by a longitudinal axis and rotatable about thelongitudinal axis, and a shaft, which is received in the housing andmovable in the direction of the axis in relation to the housing, saidlinear guide comprising a bearing assembly received in the housing forsupport of the shaft and having two bearing members and a set of rollingbodies disposed between the bearing members, with one bearing memberconstructed as bushing which is retained in the housing and defines acenter axis which is oriented out-of-alignment with respect to a normalupon a longitudinal shaft axis, and with the other bearing member havinga cup-shaped configuration to define a convex surface for support by asurface area of the shaft, wherein the bearing assembly is attached tothe housing by a swaged area of a housing portion.
 2. The linear guideof claim 1, wherein the bushing of the bearing assembly is press-fittedin a continuous radial bore of the housing, said housing portion beingpositioned adjacent to the bore and tapered inwards to form the swaging.3. The linear guide of claim 1, wherein the bearing assembly includes anaxial ball bearing.
 4. The linear guide of claim 1, wherein the bearingassembly includes a radial needle bearing.
 5. The linear guide of claim1, wherein the center axis of the bushing is shifted in parallelrelationship at an offset to the normal upon the longitudinal shaftaxis.
 6. The linear guide of claim 1, wherein the center axis of thebushing extends at an angle in relation to the normal.
 7. The linearguide of claim 1, wherein the shaft is a steering-column spindle havinga polygonal configuration, with the surface area having a concave shape,wherein at least two longitudinal sides adjoining one another incircumferential direction have each a said concave surface area.
 8. Thelinear guide of claim 7, wherein the polygonal configuration is selectedfrom the group consisting of triangular configuration, tetragonalconfiguration, and square configuration.
 9. The linear guide of claim 1,wherein the shaft is hollow or solid.
 10. The linear guide of claim 4,wherein the other bearing member has a bearing journal, said bushingbeing a needle bushing having a bottom formed with an inwardly directedconvexly arched elevation for support of an outer end surface of thebearing journal.
 11. The linear guide of claim 4, further comprising anaxial rolling bearing having a set of rolling bodies disposed between abottom of the bushing of the radial needle bearing and an outer endsurface of the other bearing member.
 12. The linear guide of claim 11,wherein the other bearing member has a T-shaped configuration with abearing journal and a running disk, which is disposed immediatelyadjacent the shaft and has the convex surface, said rolling bodies ofthe axial ball bearing and the rolling bodies of the radial needlebearing being positioned between the one bearing member and the bearingjournal.
 13. The linear guide of claim 1, wherein the housing isthin-walled and forms a pretensioning element to bias the bearingassembly, when the shaft is received in the housing.
 14. A linear guidefor transmitting a torque between a tubular housing, which is defined bya longitudinal axis and rotatable about the longitudinal axis, and ashaft, which is received in the housing and movable in the direction ofthe axis in relation to the housing, said linear guide comprising pluralaxial rolling bearings received in the housing in surroundingrelationship to the shaft, wherein the plural axial rolling bearings aredisposed in two radial planes in axial spaced-apart relationship,wherein the axial rolling bearings in each of the two radial planes haveeach two bearing members and a set of rolling bodies disposed betweenthe bearing members, with one bearing member constructed as bushingwhich is retained in the housing and defines a center axis which isshifted in parallel relationship at an offset to a normal upon alongitudinal shaft axis, and with the other bearing member having acup-shaped configuration to define a convex surface for support by asurface area of the shaft, wherein the axial roller bearings are eachattached to the housing by swaging a housing portion.
 15. A linear guidefor transmitting a torque between a tubular housing, which is defined bya longitudinal axis and rotatable about the longitudinal axis, and ashaft, which is received in the housing and movable in the direction ofthe axis in relation to the housing, said linear guide comprising pluralradial needle bearings received in the housing in surroundingrelationship to the shaft, said plural axial rolling bearings beingdisposed in two radial planes in axial spaced-apart relationship,wherein the radial needle bearings in each of the two radial planes haveeach two bearing members and a set of rolling bodies disposed betweenthe bearing members, wherein one bearing member is constructed as needlebushing which is retained in the housing and defines a center axis whichis shifted to a normal of a longitudinal shaft axis, wherein the otherbearing member has a cup-shaped configuration to define a convex surfacefor support by a surface area of the shaft, and includes a bearingjournal which is surrounded by the needle bushing, with the rollingbodies arranged in the needle bushing and constructed as needles,wherein the radial needle bearings are each attached to the housing byswaging a housing portion.